Local buses have been developed so that the system buses of a computer system can be accessed at speeds close to that of the microprocessor. Of these, the PCI local bus is now the most widely accepted and implemented expansion system. This local bus is a high performance 32-bit or 64-bit bus with multiplexed address and data lines, and is intended for use as an interconnect mechanism between highly integrated peripheral controller components, peripheral add-in cards and processor/memory systems. The bus allows burst mode data transfer and bus mastering, and is usable with many different kinds of add-in cards, such as graphical user interfaces, modems, network cards, sound, video capture and SCSI cards. Some of the cards are 32-bit, operating at 33 MHz, while others are 64-bit, operating at either 100 MHz or 133 MHz. The 32-bit bus is designated PCI, while the 64-bit is designated PCI-X. A different controller is required for each bus, such as the ICH4 32-bit controller and P64H2 64-bit controller by Intel Corporation.
Personal computer (PC) mother boards can have numerous different configurations, depending upon the type of circuit cards they are set up to receive. For example, if all of the cards for which they system is designed are 32-bit cards, then a number of receivers (commonly called “slots”), each designed to receive the 120 edge pins of a 32-bit card, would be provided on the board, along with an ICH4 controller connected to each of the slots in parallel. If, on the other hand, only 64-bit cards need to be accommodated, a different board with slots for the 368 edge pin 64-bit cards would be used, together with an appropriate number of P64H2 controllers (in general, one P64H2 controller is required for each two 64-bit cards operated at 100 MHz, and an individual controller for each 64-bit card operated at 133 MHz).
If, as is frequently the case, some combination of 32-bit and 64-bit cards are to be accommodated, separate boards with appropriate arrays of 32-bit and 64-bit slots and controllers are provided for each different combination. In general, each different board design is considered as a separate part, with separate order and fabrication sequences. Thus, it may be necessary for a manufacturer to inventory a large number of different boards, each with a different combination of slots and controllers, and to order new raw boards separately for each different design. The separate board designs can lead to a relatively large number of orders for relatively low volumes of boards each, which does not offer the opportunity to maximize volume discounts.
Different types of mother boards have conventionally been characterized by different numbers of circuit card slots associated with the ICH4 and P64H2 controllers, and also by the number of P64H2 controllers and whether their associated slots are intended for 133 MHz or 100 MHz operation. This type of characterization has resulted in a proliferation of different types of circuit boards, with separate inventories of raw boards for each type. New raw boards are generally acquired only when the stock of raw boards for one particular type of mother board needs to be replenished. Thus, while the collective number of raw circuit boards purchased for all types of mother boards over a given period of time may be large, the number of boards purchased with each individual order will generally be much smaller, with a corresponding loss of volume discounts and economies of scale. Mother boards with different configurations of slots controlled by the ICH4 and P64H2 controllers require different interconnection networks between the controllers and slots; the different interconnection networks emphasize the tendency to consider each different combination of slots as a separate part requiring a separate board inventory and fabrication process.